1. Field of the Invention
The present invention relates to an image pickup apparatus.
2. Description of the Related Art
Heretofore, it has been proposed that a variable-optical-power element be disposed in an image pickup optical system and a focal length or a focal position be changed by a function of the variable-optical-power element. This proposed method has an advantage that it is possible to omit a space or a mechanically movable component for moving a lens in an optical axis direction.
Specifically, there are proposed a liquid crystal lens system and a deformable mirror system.
As documents on a method of manufacturing a liquid crystal lens, there are Japanese Patent Application Laid-Open Nos. 2001-272646 and 2001-249348. It is described in Japanese Patent Application Laid-Open No. 10-73758 that the method can be applied to an image pickup lens regardless of a polarization direction of a light flux from an object.
Moreover, an example in which a deformable mirror is applied to the image pickup lens is described in Japanese Patent Application Laid-Open No. 2004-309684 and the like. In this proposal, the deformable mirror is provided with a function of bending the light flux in order to dispose the deformable mirror in the image pickup lens. Therefore, a mirror surface is an aspherical surface which is a so-called free-formed surface, and has a shape which is not rotationally-symmetrical about an optical axis.